Properly planning and executing Naval Patrol/Interdiction Air Directives is, IMHO, more challenging than planning any other type of air mission. The purpose of these Air Directives are to gain you control of certain sea hexes so that you can safely move your units and supply from one port hex to another port, temporary port, or mulberry hex and also to deprive your enemy of the ability to do the same. Before you learn how to properly plan these missions, you should first understand how sea hexes are controlled and the consequences for failure to do so. Accordingly, please make sure you have read all the relevant rules. The most important things to remember are:
1. A sea hex is friendly controlled if your interdiction value for that hex is 2 or greater than your opponents.
2. A sea hex is neutral if the difference between the opposing interdiction values is 1 or less.
3. A sea hex is enemy controlled if your opponents interdiction value for the hex is 2 or greater than yours.
4. The more neutral or enemy controlled sea hexes your units are naval or amphibious transported through during your Ground Movement phase, the more likley that transport/amphibious ships wil be lost and you will lose men and elements. It is therefore important that at the end of your friendly Air Phase you control all sea hexes that you plan on sea transporting units through.
5. If at the conclusion of your opponents Air Phase you are unable to trace a supply line through sea hexes from a supply source to a particular friendly port without passing through an enemy controlled sea hex, than all f riendly units tracing supply to that port will be isolated. Therefore it is important that at the end of your opponents Air Phase you can trace such a supply line through friendly controlled or neutral sea hexes.
6. Even if you control a particular sea hex, the higher the level of enemy interdiction in that hex the more likely you will lose transport ships (and therefore men and equipment) if you move through that hex. Therefore when sea transporting units it is better to move through a sea hex that is controlled by you 6:4 than it is to move through a sea hex you control 8:5.
7. So long as Auto Patrol is set to "Yes" (on) for a particular air HQ, air groups assigned to that HQ and not given other orders and not set to fly only at night will automatically fly naval patrol air directives around their airbase. This is useful for maintaining control of sea hexes in back water areas or anywhere the threat of enemy air patrol missions is negligible.